Ratio-based adaptive switching technique

ABSTRACT

A number of monochrome pages printed by a print system in a color mode and a total number of pages printed by the print system are monitored. A ratio of the number of monochrome pages printed by the print system in the color mode to the total number of pages printed by the print system is determined. The print system is switched between the color mode and a monochrome mode of the print system mode based on the ratio so as to reduce color cartridge wear of the print system and/or so as to reduce transitions between the color mode and the monochrome mode while printing monochrome pages.

BACKGROUND

Most color-capable laser printers have two modes of operation, a colormode and a monochrome mode. In the color mode, a color cartridge(typically having additive primaries cyan (“C”), magenta (“M”) andyellow (“Y”)) is engaged and available for use along with a monochromecartridge (typically black or “K”). In monochrome-only (mono or black)mode, the monochrome cartridge is engaged and available for use whilethe color cartridge is dis-engaged (also termed as “alienated”) to saveengaged wear on the color cartridge for black-only pages. Severalseconds are characteristically taken to complete a switch back and forthbetween the color and monochrome modes and this switching consequentlydelays a print-job. During this switch the color cartridge as well asother printer components may experience additional wear. Both theengaged wear and the additional wear occur with both two-cartridge(separate black and color) printers and all-in-one cartridge printers(combined black and color).

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure is better understood with reference to the followingdrawings. The elements of the drawings are not necessarily to scalerelative to each other. Rather, emphasis has instead been placed uponclearly illustrating the claimed subject matter. Furthermore, likereference numerals designate corresponding similar parts through theseveral views.

FIG. 1 is a simplified block diagram of an example print system with aratio-based adaptive switching technique illustrated by hardwarecomponents;

FIG. 2 is a simplified block diagram of the example print system of FIG.1 with a ratio-based adaptive switching technique illustrating thefunctionality of the print system in hardware and software modules;

FIG. 3 is a block diagram of an example computer readable medium withprocessor executable instructions organized into sub modules toimplement a ratio-based adaptive switching technique;

FIG. 4 is an example state transition diagram showing a current printermode on the horizontal axis and a determined cM/pN ratio on the verticalaxis;

FIG. 5 is flowchart of an example ratio-based adaptive switchingtechnique used to switch between printer modes; and

FIG. 6 is a flow chart of an example alternative ratio-based adaptiveswitching technique with additional possible operations that may beincluded to influence threshold values.

DETAILED DESCRIPTION

Because switching impacts printing performance and creates unwantednoise, users prefer minimal switching between modes and thus a colorcartridge may be engaged (de-alienated) by default. Unfortunately, insome usage patterns of a printer, when a color cartridge is engaged toprevent switching, a color cartridge may wear out before its colortoners are depleted. This premature wear-out is not desired by users ofthe printer. Accordingly, it is very difficult to keep printingperformance acceptable while at the same time minimizing unneeded wearon the color cartridges.

To address these issues, a printing system having an adaptive switchingtechnique based on a ratio of two recorded parameters that indicate wearis disclosed herein. The ratio is used to balance the optimization ofboth print-job performance and excess color cartridge wear. This dynamicratio-based adaptive switching technique is used for determining whenand how to dis-engage (alienate or switch-out) color cartridges tominimize excess wear. The two recorded parameters are the total numberof pages printed (pN) and the number of black-only monochrome pagesprinted in color mode (cM). A ratio of cM to pN (cM/pN) is computed andcompared to two thresholds separated by a hysteresis window. When thelargest threshold is exceeded then the color cartridges are dis-engaged(alienated) to preserve color cartridge life by reducing unnecessarywear when printing monochrome pages. Once the color cartridges are notprinting monochrome pages, the ratio cM/pN begins to drop. Once thelower of the two thresholds is reached, the color cartridges are engaged(de-alienated) or switched back in during monochrome printing tominimize the print-job performance impact. This ratio-based adaptiveswitching technique maintains a balance between both color and colormode monochrome printing, and color and black-only monochrome printing.More specific detail of example implementations and various possiblemodifications follow in the detailed description of the drawings.

For instance, FIG. 1 is a simplified block diagram of an example printsystem 100 with a ratio-based adaptive switching technique 10illustrated with hardware components. Print system 100 includes acomputing unit 110 and a printing unit 150. The computing unit 110 mayinclude a panel interface (Panel I/F) 108 typically coupled to a panel160, such as an LCD, LED, plasma, OLED, AM-LED, IPS, or other display toprovide visual indications of progress, options, and supply readiness toa user. Also, the computing unit 110 through and external displayinterface (EXT. D I/F) 106 typically receives one or more print-jobs 140from one or more data processors 112. Data processors may encompass apersonal computer, a laptop, cell phone, print server, cloud-basedserver, and other equivalent computer systems that process variouselectronic data into printable content. The print-jobs 140 may containmonochrome-only (e.g., black-only), color-only, or mixed monochrome andcolor data-sets. Computing unit 110 includes one or more CPUs 124 havingone or more cores capable of executing one or more software threads ofinstructions. The computing unit 110 and the printing unit 150 may betypically electronically coupled via a data bus 130 through a printinterface 112.

Computing unit 110 may include tangible, non-transitorycomputer-readable medium (CRM) 120, such as read-only memory (ROM) 122,random-accessible memory (RAM) 124 (such as DRAM and SRAM), hard diskdrives (HDD) 120, and external memories through an external interface(Ext. I/F) 128. The external interface may connect to external SCSI,ATA, USB, Firewire, network based, cloud-based, and other forms ofremote memory known to those of skill in the art. The CRM 120 containsinstructions in the form of computer executable code that when read by aprocessor, such as CPU 124, allows the processor to execute one or moresoftware routines or modules, such as ratio-based adaptive switchingtechnique 10.

CRM 120 allows for storage of one or more sets of data structures andinstructions (e.g. software, firmware, logic) expressed or utilized byany one or more of the methodologies or functions described herein. Theinstructions may also reside, completely or at least partially, with thestatic memory, the main memory, and/or within the processor duringexecution by the computing system. The main memory, ROM 122 and RAM 124and the CPU 124 memory also constitute computer readable medium 120. Theterm “computer readable medium” 120 may include single medium ormultiple media (centralized or distributed) that store the one or moreinstructions or data structures. The computer readable medium 120 may beimplemented to include, but not limited to, solid state, optical, andmagnetic media whether volatile or non-volatile. Such examples include,semiconductor memory devices (e.g. Erasable Programmable Read-OnlyMemory (EPROM), Electrically Erasable Programmable Read-only Memory(EE-PROM), and flash memory devices), magnetic discs such as internalhard drives and removable disks, magneto-optical disks, and CD-ROM(Compact Disc Read-Only Memory) and DVD (Digital Versatile Disc) disks.

The various examples described herein may include logic or severalcomponents, modules, or constituents. Modules may constitute eithersoftware modules, such as code embedded in tangible non-transitorycomputer readable medium 120) or hardware modules. A hardware module isa tangible unit capable of performing certain operations and may beconfigured or arranged in certain manners. In one example, one or moreCPUs 124 or one or more hardware modules of computing unit 110 may beconfigured by software (e.g. an application, or portion of anapplication) as a hardware module that operates to perform certainoperations as described herein.

In some examples, a hardware module may be implemented as electronicallyprogrammable. For instance, a hardware module may include dedicatedcircuitry or logic that is permanently configured (e.g. as aspecial-purpose processor, state machine, a field programmable gatearray (FPGA) or an application specific integrated circuit (ASIC) toperform certain operations. A hardware module may also includeprogrammable logic or circuitry (e.g. as encompassed within ageneral-purpose processor or other programmable processor) that istemporarily configured by software to perform certain operations. Itwill be appreciated that the decision to implement a hardware moduleelectronically in dedicated and permanently configured circuitry, or intemporarily configure circuitry (e.g. configured by software) may bedriven by cost and time considerations.

The printing unit 150 may have one or more modes of operation, such ascolor mode 154 and monochrome mode 158. In the color mode 154, each ofthe black (“K”) and color (“C”, “Y”, “M”) cartridges 152 are engaged andavailable for use in printing documents of a print-job 140. Inmonochrome mode 158, the “K” cartridge 156 is engaged and available foruse in printing while the color “C”, “Y”, “M” cartridges 157 aredis-engaged (alienated) and not available for use in printing.

The print system 100 may include one or more adaptive switchingtechniques 10 (see for instance, flowchart 500 in FIG. 5 and flowchart600 in FIG. 6 ) selectable by users or to operate automatically andapplicable for both two-part and all-in-one toner cartridge systems tominimize unneeded wear on the color cartridges 157 when they are notused during printing of monochrome pages. The various adaptive switchingtechniques 10 also improve print-job performance by minimizing whenswitching between color mode 154 and monochrome modes 158 is used. Inone adaptive switching technique 10, a ratio 306 (FIG. 3 ) is determinedby monitoring a number (cM 314, a first behavior) of black-onlymonochrome (mono) pages printed while in color mode to the total numberof pages printed (pN 302, a second behavior). This ratio 306 (cM/pN) isindicative of the unneeded wear on the color cartridge 157 components.For instance, when the ratio is near 1, then there is excess unneededwear on the color cartridges 157. When the ratio is near 0, there isminimal unneeded wear on the color cartridges 157. However, to comeclose to achieving this low ratio there may be frequent switching of thecolor cartridge 157 components in (de-alienate) and out (alienate) of aprint path of print system 100. This switching action may createundesired noise and print-job delay, thereby impacting print-job 140performance. Hence, it is difficult to minimize the amount of additionalwear on the color cartridges while keeping acceptable systemperformance.

One goal of the adaptive switching techniques 10 is to therefore tominimize the performance impact of switching between modes to when it isneeded to preserve color cartridge life when there is adequate toneravailable. Accordingly, the adaptive switching techniques 10 optimizeboth print-job performance and excess cartridge wear of the system basedon the determined ratio. The result is a balance between pages of botha) Color and Color Mode Mono, and 2) Color and Black (K)-only Mono.

FIG. 2 is a simplified block diagram of the print system 100 of FIG. 1with a ratio-based adaptive switching technique 10 illustrating thefunctionality of print system 100 in hardware and software modules orcombinations of hardware and software modules depending upon specificimplementations. Print system 100 includes computing unit 110 andprinting unit 150. Computing unit 110 includes CRM 120 with instructions220 to implement a ratio-based adaptive switching technique 10 in theform of one or more modules, such as monitor behavior module 202,determine ratio module 206 and optimize system module 204. The variousmodules may be part of a single overall module or program or may beimplemented as one or more sub-routines, object-oriented softwareobjects, or separate autonomous program modules. Further variousfunctionality of the modules may be shared, interoperate, or resideotherwise between the different modules. In one example, the computingunit 110 communicates with printing unit 150. The printing unit 150 mayinclude one or more hardware and/or software modules to implement aswitching unit 210 to switch between the color mode 154 and themonochrome mode 158 of print system 100. In some examples, the computingunit 110 may also be partially or fully implemented as part of printingunit 150. Also, the CRM 120, instructions 220, and one or more of thevarious modules to implement a ratio-based adaptive switching technique10 may also reside partially or fully in printing unit 150.

FIG. 3 is a block diagram of an example computer readable medium 120with processor executable instructions 220 organized into sub modules toimplement a ratio-based adaptive switching technique 10 that balancesprint-job performance and component wear.

In module 312, the instructions monitor a total number (pN) of printedpages 302 performed by print system 100 with both color mode 154 andmonochrome mode 158 and a number (cM) of monochrome pages performed byprint system 100 in a color mode 154. In module 314, the instructions220 determine a ratio of cM 304 to pN 302 (cM/pN) 306. In module 316,the instructions 220 select the print system 100 to select the colormode 154 when the ratio is less than a first threshold. In module 318,the instructions select the print system 100 to select a monochrome mode158 when the ratio 306 is more than second threshold. In some exampleimplementations, there may be more than one switching technique used todetermine the current printing mode as discussed below. Therefore, theprint system 100 may include more than one adaptive switching technique10 and each technique may share or include their own unique counters(cM, pN) and threshold values.

FIG. 4 is an example state transition diagram 400 showing the currentprinter mode 404 on the horizontal axis and the determined cM/pN ratio306 on the vertical axis. The current printer mode may also encompassselection a default or “home” printer mode, which could be either colormode 154 or monochrome-only mode 158. In this example, print system 100may change the default home mode to optimize for the current contenttype that users are most printing. This change of default home mode maybe the most optimal for print-job 140 performance. In some examples,however, it may be that the default home mode always remains color mode154, and that on the receipt of a monochrome-only job, the print system100 switches to monochrome-only mode 158. In other examples, the defaulthome mode may be monochrome-only mode 158 and the print system 100switches to color mode 154 when a color job arrives 456.

The vertical axis of cM/pN ratio 306 includes a first threshold 410 anda greater second threshold 412, the difference between the twothresholds create a hysteresis region 414. In general, a lower thresholdvalue indicates more switching may occur, a greater threshold valueindicates a desire for better print-job performance. To begin with, aprinter system 100 with new black 156 and color 157 cartridges maytypically initialize the start mode 406 of current printer mode 404 incolor mode 154. As various print-jobs 140 are received, including whenmonochrome job arrives 454, the computing unit 110 tracks the totalnumber of pages printed pN 302 and the number cM 304 of black-only ormonochrome pages printed in color mode 154 of the print system 100. Theratio 306 of cM to pN will increase when there is a greater number ofmonochrome pages being printed than when there are pages with colorbeing printed while in color mode 154. As more pages with color areprinted and correspondingly less monochrome pages printed, the ratio 306will decrease.

Once the ratio 306 reaches a first threshold 410 and a second threshold412, depending on the current printer mode 404 state, different actionswill occur. For instance, while in color mode 154, when a monochromejob, such as monochrome job 420 arrives while the ratio 306 is less thanthe second threshold 412, the current printer mode 404 remains in thecolor mode 154 state while the ratio 306 increases due to the monochromepages being printed while in color mode 154. However, once the ratio 306increases beyond the second threshold 412, such as by printing mixedblack and color print-jobs with more black than color pages, and then afurther monochrome job 422 arrives, the print system 100 changes thecurrent printer mode 404 to monochrome mode 158 as shown by state arrow424. While in monochrome mode 158, when monochrome print-jobs 140 arriveand are printed, the ratio 306 will decrease as the numerator cM staysconstant while the denominator pN continues to increase. Note that, whena print-job with color job 456 arrives (as shown by state arrows 428,430, and 434) the print system 100 switches to color mode 154 to allowfor the color printing.

Depending on the ratio 306 value with respect to the first threshold 410and second threshold 412, the printer may stay in color mode 154, suchas with state arrow 434, or it may return to monochrome mode 158, suchas with state arrows 430 and 428. Stated otherwise, once the ratio 306has exceeded the second threshold 412, the print system 100 will switchor transition to monochrome mode 158 upon receiving a monochromeprint-job 140. Once in the monochrome mode 158 after the secondthreshold 412 has been reached, printing of monochrome print-jobs willdecrease the ratio 306. Until the ratio 306 has decreased to the firstthreshold 410, any print-job 140 received that has a color page willcause the print system 100 to temporarily transition (as shown by statearrows 428, 430) to color mode 154 to print the color pages and thentransition back to monochrome mode 158 as the current printer mode 404to reduce wear on the color cartridge 157 components. While inmonochrome mode 158, when the ratio 306 is less than the first threshold410, any received print-job 140 with a color page will cause the currentprinter mode 404 to switch non-temporarily back to color mode 154, asshown by state arrow 434.

In some example implementations of print system 100, such as by useroption selection or based on the expected type of print-jobs to bereceived by print system 100, the current printer mode 404 may selectedto be monochrome mode 158 in alternative start mode 408. Thus, the ratio306 will stay at zero as all black-only or monochrome pages are printedin monochrome mode 158 and cM remains zero as pN increases. Once a colorjob arrives 456, the print system 100 current printer mode 404 willtransition to color mode 154 as shown by state arrow 436. The ratio 306may then continually increase as monochrome pages are printed in colormode 154. This example implementation allows for minimizing wear ofcolor cartridges 157 until an actual color job arrives 456.

In another example implementation, the module 312 includes instructions220 to have the print system 100 wait until the number of printed pagespN 302 exceeds a predetermined number before the instructions 220 inmodules 316 and 318 are executed by the processor to select the printsystem modes (i.e. color mode 154, monochrome mode 158).

In yet another example, the instructions 220 may include an additionalmodule to analyze actual usage patterns of the print system 100 andadjust one or both the first threshold 410 and the second threshold 412to reduce transitions between the color mode and the monochrome mode andthereby minimize an amount of color cartridge 157 life while the printsystem 100 prints monochrome pages. Also, the instructions 220 may alsoconsider component life within cartridges 152, such as toner and wearcomponents, and adjust one or both the first threshold 410 and thesecond threshold 412 based at least partially on the component life. Forinstance, if an estimated life of the toner remaining in a colorcartridge 157 is less than an estimated remaining life of the wearcomponents of the color cartridge 157, or the trend of the toner life isdecreasing faster than the trend of the remaining life of the wearcomponent then the second threshold 412 may be raised to keep printsystem 100 performance as the color toner will likely run out before thewear components wear out. Alternatively, the first threshold 410 may beraised to reduce the hysteresis region to allow print system 100 todefault back to color mode more quickly when a color job arrives 456 asthe color cartridge 157 may take on more wear before the color toner isexpected to expire. In yet another example, both the first threshold 410and the second threshold 412 may be raised to emphasize printperformance over component wear.

If the estimated wear life is less than the estimated toner life and/orthe trend is that the estimated wear life is decreasing faster than theestimated toner life, either or both the first threshold 410 and thesecond threshold 412 may be reduced to cause the print system 100 tohave the current printer mode 404 be in monochrome mode 158 as it wouldappear from the usage patterns that most current print-jobs aremonochrome and it would be prudent to stay in the monochrome mode 158 asa default to emphasize decreased component wear over print performance.

In fact, some example implementations may include a learning system tocontinually analyze usage patterns of the print system 100 and have thelearning system dynamically optimize performance behavior based onreal-time usage of the print system 100. For instance, normally, whenthe second threshold 412 is reached and it is determined to switch tomonochrome mode 158 from color mode 154, it may be assumed that theprint system 100 will switch back to color mode 154 eventually.Therefore, one may assume that any switch from color mode 154 tomonochrome mode 158 will also have a monochrome mode 158 to color mode154 switch as well. Accordingly, if a final page of a print-job 140 isoften monochrome, one can relax this assumption and get more aggressiveto lower the setting of the second threshold 412 and perhaps also thefirst threshold 410 to trigger a faster change to monochrome mode 158because the overall cost to print-job performance is likely to be loweras it appears most print-jobs are monochrome only or mostly monochrome.

For print system 100, an example learning system may thus detect thatthe final page before a spin-down of the paper feed components is oftenor usually monochrome. Perhaps in this situation, a user is printing aset of letters where the first page of a letter has a color logo and allfollowing pages of the letter are monochrome. Thus, most of the pages ofthe set of letters may be assumed to be monochrome and as such, a switchto color mode 154 to print the color logo and a quick switch back tomonochrome mode 158 for the monochrome pages can reduce wear on thecolor components without significantly reducing the overall print system100 performance. Consequently, a learning system may look foropportunistic usage patterns and adjust the threshold levels accordinglyto balance the print-job performance and cartridge wear to match moreclosely current usage patterns of print system 100.

Therefore, a print system 100 may include a printing unit 150 to printan image on a recording medium in a color mode 154 or a monochrome mode158. The printing unit 150 may include a switching unit 210 to switchthe printing unit 150 between the color mode 152 and the monochrome mode158. A computing unit 110 is configured with instructions to performoperations. Such operations include instructions to monitor a number(cM) 304 of monochrome pages printed in the color mode 154 and a totalnumber (pN) 302 of printed pages. The instructions also determine aratio 306 cM/pN that is indicative of unnecessary excess cartridge 156,157 wear of the print system. The instructions then optimize print-job140 performance and cartridge 156, 157 wear of the print system based onthe determined ratio 306. In some examples, the computing unit 110 doesnot optimize until at least a predetermined total number of printedpages pN 302 has accumulated to better derive an accurate understandingof a standard usage of the print system 100. In yet other examples, thecomputing unit 110 optimizes by minimizing both the number oftransitions between the color mode 154 and the monochrome mode 158 andthe life of a color cartridge 157 in the print system 100 that is usedwhile printing monochrome pages. As noted above, the computing unit 110may also be configured to perform a learning system to allow fordynamically optimizing the print-job performance and the cartridge wearbased on real-time usage of the print system 100. Accordingly, the printsystem 100 may include more than one method of switching between colormode 154 and monochrome mode 158 and each method may include their ownunique counters and thresholds.

FIG. 5 is flowchart 500 of an example ratio-based adaptive switchingtechnique 10 to change between current printer modes. When the adaptiveswitching technique 10 begins in start block 502, it begins to monitorprint system 100 for the total number of printed pages, pN 302, in bothcolor mode 154 and monochrome mode 158 as well as the number ofmonochrome pages, cM 304, printed in color mode 154. In decision block506, a ratio of cM/pN is determined whether it is less than or not afirst threshold 410 and if so, selecting the color mode 154 of the printsystem 100 in block 508. If not less, then in decision block 510 theratio cM/pN is determined whether it is greater or not than a secondthreshold 412 and if so, selecting the monochrome mode 158 of the printsystem 100 in block 512. If not greater, and after the color ormonochrome modes have been selected in blocks 508, 512, respectively,the adaptive switching technique 500 continues to block 514 to keep thecurrent printer mode 404 and then back to block 504 to continuemonitoring pN 302 and cM 304 and checking if the ratio 306 of cM/pN tothe first and second thresholds in decision blocks 506, 510.

FIG. 6 is a flow chart 600 of an example alternative adaptive switchingtechnique 10 with additional possible operations that may be included orused to influence the first and second threshold values. For instance,once the alternative adaptive switching technique 10 begins in startblock 602, it similarly monitors pN 302 and cM 304 in block 504 asdescribed for FIG. 5 's flow chart. However, before checking the ratio306 of cM/pN to the first threshold 410 and the second threshold 412 indecision blocks 506 and 510, in decision block 604 the alternativeadaptive switching technique 600 waits until the total number of printedpages pN 302 exceeds a predetermined number before proceeding todetermining if the ratio 306 against the first and second thresholds inblocks 506, 508, 510, 512, and 514 as described for FIG. 5 . Therefore,an alternative adaptive switching technique 10 may wait until the numberof printed pages exceeds a predetermined number before the elements ofdetermining are performed.

In some implementations, an alternative adaptive switching technique 10may include a learning module that in block 606 allows for monitoringreal-time usage patterns of the print system 100 and in block 608modifying at least one of the first threshold 410 and the secondthreshold 412 to minimize at least one of cartridge 156, 157 wear oroptimize print-job time performance of the print system 100 based on thereal-time usage patterns. Block 608 may in some implementations in block610 also check the level or age of at least one component in a cartridgeof the print system 100 and then modify at least one of the firstthreshold and the second threshold based on the level or age of at leastone component in a cartridge of the print system. For example, if thecolor toner has an expiration date that is soon approaching and thetimeframe to the expiration date is less than the expected time for wearout of the color cartridge 157 or the color toner level is low, then thefirst and second thresholds may be increased to keep emphasizingprint-job performance as the color cartridge will need to be replacesoon anyway.

In another implementation, the alternative adaptive switching technique10 may include in block 612 of first selecting the monochrome mode 158as the current printer mode 404 of the print system 100. Then in block614 print-jobs 140 for the print system 100 are received. In decisionblock 616, the print-job 140 is checked to see if it is a colorprint-job and when a color page is to be printed and if so in block 618the color mode 154 is selected as the current printer mode 404 for theremaining color print-job 140 before returning to block 504 andmonitoring of the behavior of print system 100 using the pN and cMvariables. If not, then decision block 616 proceeds to block 514 to keepthe current printer mode 404.

In summary, the adaptive switching techniques 10 and hardware andsoftware logic discussed above allows for managing the wear life an anyprint system 100 that has at least two possible methods of behavior(e.g. total number of printed pages (pN) 302 and number of monochromepages printed in color mode (cM) 304) that may be controlled and/oroptimized based on the real-time usage of the print system 100. In thegiven examples, a ratio 306 of cM to pN (cM/pN) may be controlledthrough use of thresholds which may be passively set or activelyadjusted to achieve a balance between the print-job performance andreduced wear of color cartridge components based on usage, usagepatterns, component life, amount of toner. Allowing for activelyadjusted thresholds, the entire print system 100 may be analyzed andreal-use print usage patterns determined. These print usage patterns maythen be used to vigorously adjust the thresholds and thus the behaviorof the print system 100 may be dynamically optimized for real-usepatterns along with the real-time usage.

While the claimed subject matter has been particularly shown anddescribed with reference to the foregoing examples, those skilled in theart will understand that many variations may be made therein withoutdeparting from the intended scope of subject matter in the followingclaims. This description should be understood to include all novel andnon-obvious combinations of elements described herein, and claims may bepresented in this or a later application to any novel and non-obviouscombination of these elements. The foregoing examples are illustrative,and no single feature or element is central to all possible combinationsthat may be claimed in this or a later application. Where the claimsrecite “a” or “a first” element of the equivalent thereof, such claimsshould be understood to include incorporation of one or more suchelements, neither requiring nor excluding two or more such elements.

What is claimed is:
 1. A print system comprising: printing hardware toprint monochrome pages in a color mode or a monochrome mode; aprocessor; and a memory storing instructions executable by the processorto: monitor a number of already printed monochrome pages printed in thecolor mode and a total number of already printed pages; determine aratio of the number of already printed monochrome pages printed in thecolor mode to the total number of already printed pages; and switchbetween the color mode and the monochrome mode based on the ratio so asto reduce transitions between the color mode and the monochrome modewhile printing the monochrome pages.
 2. The print system of claim 1,wherein the instructions are executable by the processor to switchbetween the color mode and the monochrome mode based on the ratio so asto further reduce color cartridge wear of the print system.
 3. The printsystem of claim 1, wherein the printing hardware comprises: a colorcartridge that is de-alienated in the color mode but not used in thecolor mode to print the monochrome pages, and that is alienated in themonochrome mode and not used in the monochrome mode to print themonochrome pages; and a black cartridge to print the monochrome pages inboth the monochrome mode and the color mode.
 4. The print system ofclaim 1, wherein the processor is to switch between the color mode andthe monochrome mode in a hysteretic manner.
 5. The print system of claim1, wherein the instructions are executable by the processor to switchbetween the color mode and the monochrome mode by: while in the colormode, switching to the monochrome mode upon receiving a monochrome printjob if the ratio is greater than a threshold, and then remaining in themonochrome mode upon completion of the monochrome print job; and whilein the color mode, remaining in the color mode upon receiving themonochrome print job if the ratio is less than the threshold.
 6. Theprint system of claim 5, wherein the threshold is a second threshold,and wherein the instructions are executable by the processor to switchbetween the color mode and the monochrome mode by further: while in themonochrome mode, temporarily switching to the color mode upon receivinga color print job if the ratio is greater than a first threshold lessthan the second threshold, and then switching back to the monochromemode upon completion of the color print job; while in the monochromemode, switching to the color mode upon receiving the color print job ifthe ratio is less than the first threshold, and then remaining in thecolor mode upon completion of the color print job; and while in themonochrome mode, remaining in the monochrome mode upon receiving themonochrome print job.
 7. The print system of claim 1, wherein theinstructions are executable by the processor to switch between the colormode and the monochrome mode by: while in the monochrome mode,temporarily switching to the color mode upon receiving a color print jobif the ratio is greater than a threshold, and then switching back to themonochrome mode upon completion of the color print job; while in themonochrome mode, switching to the color mode upon receiving the colorprint job if the ratio is less than the threshold, and then remaining inthe color mode upon completion of the color print job; and while in themonochrome mode, remaining in the monochrome mode upon receiving themonochrome print job.
 8. The print system of claim 7, wherein thethreshold is a first threshold, and wherein the instructions areexecutable by the processor to switch between the color mode and themonochrome mode by further: while in the color mode, switching to themonochrome mode upon receiving a monochrome print job if the ratio isgreater than a second threshold greater than the first threshold, andthen remaining in the monochrome mode upon completion of the monochromeprint job; and while in the color mode, remaining in the color mode uponreceiving the monochrome print job if the ratio is less than the secondthreshold.
 9. A non-transitory computer-readable medium storinginstructions executable by a processor to: monitor a number of alreadyprinted monochrome pages printed by a print system in a color mode and atotal number of already printed pages printed by the print system;determine a ratio of the number of already printed monochrome pagesprinted in the color mode to the total number of already printed pages;and switch the print system between the color mode and a monochrome modeof the print system mode based on the ratio so as to reduce colorcartridge wear of the print system while printing monochrome pages bythe print system.
 10. The non-transitory computer-readable medium ofclaim 9, wherein the processor is to switch the print system between thecolor mode and the monochrome mode based on the ratio so as to furtherreduce transitions between the color mode and the monochrome mode whilethe print system is printing monochrome pages.
 11. The non-transitorycomputer-readable medium of claim 9, wherein the processor is to switchthe print system between the color mode and the monochrome mode in ahysteretic manner.
 12. The non-transitory computer-readable medium ofclaim 9, wherein the processor is to switch the print system between thecolor mode and the monochrome mode by: when the print system is in thecolor mode, switching the print system to the monochrome mode uponreceiving a monochrome print job if the ratio is greater than athreshold, and then causing the print system to remain in the monochromemode upon completion of the monochrome print job; and when the printsystem is in the color mode, causing the print system to remain in thecolor mode upon receiving the monochrome print job if the ratio is lessthan the threshold.
 13. The non-transitory computer-readable medium ofclaim 12, wherein the threshold is a second threshold, and wherein theprocessor is to switch the print system between the color mode and themonochrome mode by further: when the print system is in the monochromemode, temporarily switching the print system to the color mode uponreceiving a color print job if the ratio is greater than a firstthreshold less than the second threshold, and then switching the printsystem back to the monochrome mode upon completion of the color printjob; when the print system is in the monochrome mode, switching theprint system to the color mode upon receiving the color print job if theratio is less than the first threshold, and then having the print systemremain in the color mode upon completion of the color print job; andwhen the print system is in the monochrome mode, having the print systemremain in the monochrome mode upon receiving the monochrome print job.14. The non-transitory computer-readable medium of claim 9, wherein theprocessor is to switch the print system between the color mode and themonochrome mode by: when the print system is in the monochrome mode,temporarily switching the print system to the color mode upon receivinga color print job if the ratio is greater than a threshold, and thenswitching the print system back to the monochrome mode upon completionof the color print job; when the print system is in the monochrome mode,switching the print system to the color mode upon receiving the colorprint job if the ratio is less than the threshold, and then having theprint system remain in the color mode upon completion of the color printjob; and when the print system is in the monochrome mode, having theprint system remain in the monochrome mode upon receiving the monochromeprint job.
 15. The non-transitory computer-readable medium of claim 14,wherein the threshold is a first threshold, and wherein the processor isto switch the print system between the color mode and the monochromemode to further: when the print system is in the color mode, temporarilyswitching the print system to the monochrome mode upon receiving amonochrome print job if the ratio is greater than a second thresholdgreater than the first threshold, and then having the print systemremain in the monochrome mode upon completion of the monochrome printjob; and when the print system is in the color mode, having the printsystem remain in the color mode upon receiving the monochrome print jobif the ratio is less than the second threshold.
 16. A method comprising:receiving, by a print system having a color mode and a monochrome mode,a monochrome print job; if the print system is in the color mode and aratio of a number of already printed monochrome pages printed by theprint system in the color mode to a total number of already printedpages printed by the print system is greater than a threshold, switchingto the monochrome mode before printing the monochrome print job andremaining in the monochrome mode after printing the monochrome printjob; if the print system is in the color mode and the ratio is less thanthe threshold, remaining in the color mode while and after printing themonochrome print job; if the print system is in the monochrome mode,remaining in the monochrome while and after printing the monochromeprint job; and printing the monochrome print job.
 17. The method ofclaim 16, wherein the threshold is a second threshold, the methodfurther comprising: receiving a color print job; if the print system isin the monochrome mode and the ratio is greater than a first thresholdless than the second threshold, temporarily switching to the color modebefore printing the color print job and then switching back to themonochrome mode after printing the color print job; if the print systemis in the monochrome mode and the ratio is less than the firstthreshold, switching to the color mode before printing the color modeand remaining in the color mode after printing the color print job; andprinting the color print job.
 18. The method of claim 17, wherein themethod reduces transitions between the color mode and the monochromemode while printing monochrome pages.
 19. The method of claim 18,wherein the method reduces color cartridge wear of the print system. 20.The method of claim 17, wherein the method reduces color cartridge wearof the print system.